Method for separating hydrocarbons and making mercaptans



C- 15,' 1945. D. E. BADERTscHER Erm.' 2,333,771

METHOD FOR SEPARATING HYDROCARBONS AND MAKING MERCAPTANS 2 Sheets-Sheet l Filed June 29, 1943 A TTORNE Y.

@ci i6, 1945- D. E. BADERTscHER :TAL I 2,385,771

METHOD AFOR SEPARATING HYDROCARBONS AND MAKING MERCAPTANS Filed June 29, 194s 2 sheets-snee: '2

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A TTORNE Y.

Patented Oct. i6, 1945 METHOD FOR SEPARATING HYDROCAR- BONS AND MAKING MERCPTANS Darwin E. Badertscher, Woodbury, N. J., Harry L. Coonradt, Camp Lee, Va., and Duncan J; Crowley, Penns Grove, N. J., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York Application June 29, 1943, Serial No. 492,669 (c1. 26o-sos) resins and the process of the present invention Claims.

This application is a continuation-impart of our application Serial No. 461,116, led October l 7, 1942, and has to do with a, selective catalytic method for effecting the separation of certain olens from hydrocarbon mixtures. More speciflcally, the present invention has to do' with a vapor phase, catalytic treatment of a hydrocarbon mixture with HzS whereby only those hydrocarbons of a sub-class of olelns, hereinafter defined as the tertiary base oleiins, are converted to their corresponding mercaptans.

It is well known to those familiar with the art that olefins will react with HzS in the presence of various catalysts to form mercaptans. For example, it has been suggested that olens of at least eight carbon atoms will react in the liquid phase in the presence of certain catalysts, at time intervals of from 6 to 72 hours, to form sulfur-containing compounds including suldes and mercaptans. The present invention distinguishes over the foregoing in that our catalytic treatment is carried out in the vapor phase with a very brief contact time which may vary .from a fraction of a second to about several minutes. Another fundamental distinction between previously proposed processes and the novel process of the present invention is predicated upon our discovery that the catalytic` process contemplated herein is selective for the conversion of certain oleflns to their corresponding mercaptans. For example, the present invention is based upon the discovery that the C-4 and C-5 tertiary base olens, isobutylene, trimethyl ethylene and unsymmetrical methyl ethylv ethylene (of which the latter two are tertiary base amylenes), contained in a mixture of hydrocarbons are converted to their corresponding tertiary mercaptans when the hydrocarbon mixture in the vapor phase and in admixture with HzS is passed over a suitable catalyst with the temperature of the catalyst or reaction zone maintained within certain preferred limits, depending upon the nature of the catalyst, the pressure in the reaction zone, etc.

Accordingly, the process of the present invention may be employed to treat a mixture of hydrocarbons for ultimate use in an operation where the tertiary base olefins, such as isobutylene and tertiary base amylenes, are harmful contaminants, and to effect the removal of such contaminants, at the same time producing' may be used to provide a butene mixture devoid of isobutylene for use in such resinlfying reaction. l

Tertiary base olefins are dened herein as those olens characterized by the presence of the tertiary olefin linkage R2C=C where R is a low molecular Weight alkyl group, such as methyl. Typical members of this class, and preferred herein, are lsobutylene, (H3C)2C=CH2, and trimethyl ethylene (H3C)2C=CCH3 The present invention also provides a highly eiective and economical method for obtaining the individual tertiar'ymercaptan from its corresponding tertiary base olefin, i. e., tertiary butyl mercaptan from isobutylene, and tertiary amyl mercaptan from trimethyl ethylene and unsymmetrical methyl ethyl ethylene, respectively. These tertiary mercaptans may be obtained asv an incident to the separation of the corresponding tertiary base oleiins from a hydrocarbon mixture as aforesaid, or they may be obtained by the vapor phase reaction of the pure tertiary base olefin with hydrogen sulde under simil-ar conditions in the same catalytic environment.

The catalysts which we have found to be effective for the purposes of this invention are the following: acids and thioacids of phosphorus and their anhydrides and thioanhydrides, elementary I(red) phosphorus, sulfuric acid and sulfonic acids, non-plastic clay-type catalysts typied by fullers earth, alumina-silica type synthetic catalysts and halogenated acids, such as trichloracetic, etc. For the purposes of the present invention, preference is given herein to elemental phosphorus, a particularly preferred form of which is red phosphorus; other catalysts are made the subject matter of companion applications. There is. little, if any, diminution in the eifectiveness of elemental phosphorus as used herein, although freshphosphorus is preferred. It is also preferred that the catalytic treatment be carried out in the absence of moisture. Therefore, it is desirable to dry the gases prior to contacting them with the catalyst. The drying of the gases prior to introduction into the reactor presents no diiiculties and is a routine procedure to those familiarl with the chemical and petroleum arts.

We have discovered that the reaction of hydrogen sulde with a tertiary base olefin to form a tertiary mercaptan by the process contemplated description taken with accompanying drawings, A

which are chosen for illustrative purposes only and in which Figure 1 is a diagrammatic view illustrating one form of apparatus which may be employed in practicing the process of this invention; Figure 2 is a sectional elevation showing in enlarged detail a typical form of reactor which may be employed in the system shown in Figure 1; and Figure 3 is a graph with a curve showing the effect of temperature variations upon the yield of tertiary butyl mercaptan in the process contemplated herein.

In Figure 1, reference numeral II indicates a reactor which is shown in Figure 2 as embodying a shell I2 which may be of circular or other suitable cross-sectional shape, such shell being provided near its top with a partition plate I3, having a plurality of openings I4, which receive the upper ends of tubes I5 secured. therein in any suitable manner, such as welding (not shown). The lower ends of the tubes I5 are supported in openings I6 through a bottom partition plate I1 secured near the bottom of the shell I2 in any suitable manner so as to form a chamber I8 in the shell between plates I1 and I3. For the purpose of controlling the temperature within the tubes I5, a suitable heat exchange medium is circulated through the chamber I8 from an inlet 20 to an outlet 2I.

The top of the chamber or shell I2 is provided with a cover 22, which with the top partition plate' I3 forms a chamber 23 in the top of the shell adapted to receive reaction vapors through an inlet 24, winch vapors enter the various tubes from the chamber 23, as indicated by the arrows. The bottom of the shell I2 is provided with a bottom cover 25, through which the products of reaction pass from the tubes I5 into the product outlet 26.

The bottoms of the various tubes I5 are provided with a suitable mesh material to support a body of catalyst indicated by the stippling in Figure 2 within these tubes. This mesh material may be supported in any suitable manner and, as shown in Figure 2, comprises a screen supported beneath the bottom plate I1 by a similarly perforated plate I1'.

As aforesaid, the reaction contemplated herein is quite sensitive to temperature control; and although the length and size of the reaction tubes I5 and the relation between the total volume of the chamber I8 and the volume within such chamber which is occupied by the reaction tubes may be varied over relatively wide limits. it is to be understood that the relationship between these various factors, the temperature of the heat exchange medium, and the rate at which heat exchange medium is circulated through the chamber I8 should be so adjusted as to maintain the temperature in the reaction zones of the various catalyst tubes I5 within the range for most eilicient operation, as will be hereinafter discussed.

Referring back to Figure 1: reference numeral I0 indicates a conduit adapted to carry hydrocarbons through a meter M into the reactor inlet conduit 24. This conduit is shown as passing through a pre-heater or vaporizer 32 through which a hot heat exchange medium is circulated by means of connections 33 and 33'. Hydrogen sulflde is introduced into the system through the valved connection 35 and a meter M', such hydrogen sulde Abeing optionally introduced into the inlet 24 on either side of the vaporizer 32 by means of valved connection 3B or 3B.

With regard to the vaporizer or pre-heater 32, it is to be understood that other suitable means may -be provided for insuring that the reactants are in the vapor phase when they pass into the catalyst tubes in the reactor. For example, it may be found, particularly after the reaction has been started, that there is sufficient heat in the reactor itself to effect this vaporization or heater coils may be provided in the chamber 23, as will readily appear to those skilled in the art.

Suitable means for controlling the temperature of the heat exchange medium entering the reactorthrough inlet 20 are indicated by reference numeral 40. The temperature-control means 40 may be any suitable heat exchange device and can be either manually or automatically operated in any manner well known to those skilled in the art. Also, if desired, the heat exchange medium may be recirculated from the outlet 2| through the temperature control 40 'to the inlet 20 as will be obvious to those skilled in the art. Any suitable heat exchange medium, such as water, may be employed to control the temperature in the chamber I8 of reactor II.

Reference numeral 4I indicates a cooler or condenser through which the product-outlet conduit 25 passes irito conduit section 26', which opens into a sealed receiving chamber 21. The cooler or condenser l4I is provided with an inlet 42 equipped with temperature-controlling means 43 and with a heat exchange medium-outlet connection 44. The temperature of the cooler 4I may be controlled through the control 43 so as to condense substantially all of the mercaptan which can then be withdrawn together with the polymerization products of reaction from the sealed chamber 21 through a valved liquid-outlet connection 45, or such temperature in the cooler 4I may be controlled so that only the high boiling products are condensed, substantially all of the mercaptan together with the hydrogen sulde and hydrocarbon gases being conducted in such case from the sealed chamber 21 through a vapor-outlet conduit 41 to the bottom of a scrubbing tower 48.

The top of the scrubbing tower 48 is provided with a gas vent 50 and an inlet conduit 5I for a scrubbing solution such as aqueous caustic soda. The bottom of the scrubber 48 has an outlet 52 which connects with the bottom of a still or stripper 54. Outlet connection 52 is equipped with a drainage valve 53. The still or stripper 54 is shown as being equipped with a high-pressure steam coil or other suitable source of heat 55 and has an outlet 56 which connects -through a condenser 51 with a separator 58. The separator 58 is provided with a valved mercaptan outlet 59, a gauge glass 13 to facilitate removal o f the mercaptan, and a valved water outlet 80. The water outlet 60 connects through a valve 5I with a water return pipe 62, which in turn is shown as connecting with the caustic reservoir 51. The

still 54 is shown as being equipped with a caustic outlet conduit 64 which includes a liquid caustic well 64', the purpose of which is to prevent mercaptan vapor froml leaving still 54 by the conduit 64. Caustic passes through conduit 64 to a caustic cooler 65 and exits therefrom through outlet 66 to the caustic reservoir 61. 'I'he caustic reservoir is tted with a drainage means B8. The

caustic reservoir is also equipped with a conduit 69 which connects with the intake side of a pump 53. .The discharge side of pump 63 is shown as connecting with inlet conduit I of scrubber 48. Means indicated at are provided for adding fresh caustic when desired; and means indicated at 1I are provided for adding fresh water to the 1 and 2, the tertiary base olefin, either alone orin admixture with other hydrocarbons, and the hydrogen sulfide are metered into the system through meters `M and M'. 'I'he proportions of these two reactants may be varied over relatively wide limits, but for optimum results it is preferred that these proportions be such that the hydrogen sulfide be slightly in excess of the molar equivalent required to react with the tertiary base olefin present.

The admixture of hydrocarbon and HzS is introduced into the reactor II in the vapor phase, as by passing the hydrocarbon through the vaporizer 32 prior to admixture with HzS. Upon entering the reactor II, the hydrocarbon-Has vapor mixture passes through the catalyst tubes I5 where it contacts the catalyst for a short period of time. It is a. feature of the process contemplated herein that the period of catalyst contact is very short. With a catalyst of the type described hereinabove, contact times of from about a fraction of a second to about several minutes serve the purposes of this invention, but in general, a contact time of a few seconds is preferred. The temperature of the heat transfer medium in chamber I8 is controlled by the temperature control 40 so that the temperature of the catalystzone within the tubes I5 is maintained within the range that will give the desired conversion. As aforesaid, the process contemplated herein is quite sensitive to temperature. We have found, for example, that the process is operative between the limits of atmospheric temperature (at about 25 C.) and about 175 C., but for optimum conversion a more closely dened range of temperature is necessary. This will be discussed in further detail hereinafter.

When in contact with the catalyst in the catalyst tubes I5 under the conditions described herein, the tertiary base olefin reacts with the hydrogen sulfide in the reaction mixture to form the corresponding tertiary mercaptan. For example, when the hydrocarbon used is isobutylene, tertiary butyl mercaptan is formed and also a small amount of higher boiling materials which are mainly polymers of isobutylene. Thus, the effluent gases leaving the reactor Il through discharge conduit 28 contain tertiary butyl mercaptan, high boiling materials, traces of unreacted HzS and traces of unreacted isobutylene. Similarly, when the hydrocarbon used is a tertiary base amylene, a tertiary amyl mercaptan is formed and the eflluent gases Will contain unreacted HzS, unreacted tertiary baseamylene and polymers of said amylene in addition to this mercaptan. When the hydrocarbon used is a hydrocarbon mixture containing a tertiary base olefin (or tertiary base olens), such as for example isobutylene, secondary oleiins, normal oleflns, and saturatedhydrocarbons, only the tertiary base olefin (or tertiary base olens) is converted to the corresponding mercaptan. Other hydrocarbons in the mixture are uneected by contact with the catalyst and HzS. With such a hydrocarbon mixture, the effluent gases contain tertiary butyl mercaptan, higher boiling materials which are predominantly polymers of isobutylene, traces of unreacted HzS and unreacted isobutylene, and unreacted hydrocarbons. such as normal oleflns, secondary olens and saturated hydrocarbons.

In either case, the eliuent gases flow through the discharge conduit 26 to the Acondenser 4I. As aforesaid, the temperature of the condenser may be maintained such that only the high boiling products are condensed, in which case, the condensate flows into the sealed chamber 21 and from which it can then be withdrawn through the outlet connection 45. The unreacted hydrocarbons, unreacted HzS and the tertiary mercaptan, such as tertiary butyl mercaptan, are

not condensed When'such a temperature is main` tained in the condenser 4I, and iiow through the vapor-outlet conduit 41 to the bottom of the scrubbing tower 48. If desired, the temperature of the condenser 4I may be adjusted so that the greater portion of the tertiary butyl mercaptan is condenser along with the high boiling materials. This condensate Withdrawn through connection 45 may then be distilled in a suitable distillation tower (not shown) to separate the tertiary mercaptan from the polymerization products.

The uncondensed portion of the reaction mixture rises in the scrubber 48-and contacts a downstream of scrubbing solution, such as aqueous caustic soda whereupon tertiary mercaptan (butyl or amyl or both, depending on the tertiary base olei'ln or oleflns in the charge) and hydrogen sulde are converted respectively to the corresponding soluble alkali mercaptide and alkali sulfide or hydrosulfide. The unreacted hydrocarbons are unaiected by the caustic soda and are removed through the gas vent 50 from which they may be conducted to another operation or treatment such as alkylation, polymerization, or the like. The alkali mercaptide and alkali sulde or hydrosulde in caustic solution pass out of the scrubber 48 through the outlet connection 52 to the still 54. High-pressure steam or other heating medium passes through the coil 55 in the still 54, thereby heating the-caustic solution to an elevated temperature. On heating the caustic solution, the alkali mercaptide is converted to the corresponding tertiary butyl or tertiary amyl mercaptan which, along with some water, distills from the solution. The tertiary mercaptan-water vapors rise to the outlet line 5B, ow therethrough to the condenser 51 where they are condensed and from which the condensate flows to the separator 5B. The condensate separates herein (58) into an upper layer of mercaptan, and lower layer of water. The mercaptan layer is Withdrawn through the valved outlet 59 to storage or other process, or processes, a. gauge glass 13 being provided to facilitate the mercaptan withdrawal.

It will be apparent from the foregoing that when the original hydrocarbon mixture contains a mixture of the preferred tertiary base olens, isobutylene and trimethyi ethylene, for example,

4- the mercaptan layer withdrawn through the valved outlet I9 will be a mixture of tertiary butyl and tertiary amyl mercaptans. These mercaptans can then be separated from each other by suitable separation means. such as by distillation (means not shown).

The lower water layer is allowed to drain from the bottom of the separator 58, through the water outlet 60. It is recombined, in passing through the valve il and the water-return pipe 62, with the caustic solution which has been discharged from the still 54. This caustic solution has passed through conduit 64, well 64", the cooler 65, conduit i6 to caustic reservoir $1. This cold caustic solution which contains some alkali sulfide, combined with water from the separator 58 is pumped by means ofthe pump 63 to the caustic scrubber Il through the inlet conduit 5|.' If,

however, said caustic solution from the still 5| tends to accumulate an,appreciable amount of alkali sulfide, it can be removed from the system by means of the drain 68, and can be replaced with a desired amount of fresh caustic through the means 10.` This is necessary'when an appreciable amount of unreacted HzS is present in the emuent gases from the reactor Il and which reacts with caustic soda in the scrubber 48 to form alkali suliide. If it is, necessary to introduce additional water into the system to add to the caustic solution cooled in the cooler 65, fresh Water can be introduced through the means 1I.

The selective action of HzS upon tertiary base oleflns, such as isobutylene and isoamylenes', is influenced by a number of factors such as temperature, pressure, contact time and rate of flow of reactants, proportions of reactants, etc. As we have previously indicated, temperature is the most important and most critical of these infiuencing factors. The reaction cf the tertiary base olen, such as isobutylene or isoamylenes, and hydrogen sulfide whereby the corresponding tertiary mercaptan is formed is slightly exothermic. Therefore, in order that the temperature of the reaction mixture be controlled within the desired limits, the heat of reaction should be uniformly and readily withdrawn from the reaction zone. This may be accomplished by a proper control of the temperature and rate of flow of the heat transfer medium in the reactor. The sensitivity 'of this reaction to temperature in the presence of red phosphorus is illustrated by the curve in Figure 3.

Referring now to Figure 3, the curve is a temperature-yield curve with temperature plotted along the abscissa and yield of tertiary butyl mercaptan plotted along the ordinate. Each point on the curve represents a single preparation of tertiary butyl mercaptan from isobutylene and slope of the curve from about 55 C. to about 100 C. indicates that the process is operative to about temperatures of the order of 200 C. Thus, it appears that the operative temperature range is from about 25 C. to about'200 C. A quantity of 26 grams of elemental.(red) phosphorus deposited on 75 grams of granulated wood charcoal, was used; this occupied about 250 oc. of

'the catalyst tube. It is seen that at'about 25 C. y

a yield of about 10% is obtained. The yield increases with increase in temperature until the maximum yield-about 70%-is obtained in the neighborhood of 55 C. Thereafter, further increase of temperature makes for smaller yields until at about 95 C., the yield is only about 45%, and at about 175 C., the slope of the curve indicates that the yield is only about 5%. For practical purposes where yields of and greater are desired, the curve indicates that temperatures within the range of about 35 C. to about 85 C. may be used. Y

While the curve was obtained with the operating conditions described abovel it will be understoodthat the slope and breadth of the curve may change with changes in one or more operating conditions. For example, various proportions of reactants may be used instead oi three liters of each gas, hydrogen sulfide and isobutylene. In general, however, it appears that the curve substantially represents the catalytic activity of elementary phosphorus in the conversion of the C-4 and C-5 tertiary base olefins to their corresponding tertiary mercaptans.

It is one feature of this invention that high pressures are not required. On the contrary, atmospheric or, at most, pressures only slightly greater than atmospheric are used. In order that the reaction be carried out in the vapor phase, it is necessary that the pressure be less than that pressure at which liquefaction or the hydrocarbon would occur at the operating temhydrogen sulfide under the following conditions which are similar to those described hereinabove. A reaction chamber containing a single catalyst tube, inside diameter 22 mm., was used. In each run, three liters per hour of each gas, isobutylene and hydrogen sulfide, were employed. Each run was continuous and varied in duration from 4 to about '7.7 hours, with contact times from about 4.0 minutes' to about 5.0 minutes, which was influenced by temperature, catalyst volume, etc. Each yield of tertiary butyl mercaptan 'was based upon that fraction of reaction product boiling from 63 C. to 66 C. at atmospheric pressure.

The curve clearly shows that the process contemplated herein with elemental (red) phosphorus as the catalyst is operative over the temperature range of about 25 C. to 100 C. and the perature. It will readily1 be seen that the use of pressures from about atmospheric to about 4 atmospheres are not such as to require the use of expensive high-pressure reaction chambers. This, of course, is a decided economic advantage.

As aforesaid, the proportions of reactants for our process obviously can be varied considerably. Theoretically, the optimum vmolar ratio of tertiary base olefin to hydrogen sulfide would be 1:1. In some cases, however, maximum yields are obtained when a slight excess of HzS is used. Tertiary base olens are notorious for their tendency to polymerize and this polymerization reaction tends to compete with the addition reaction with the resultant formation of high boiling poly tertiary base oleflns. An excess of HzS, therefore will increase the yield of mercaptan by affording greater opportunity for the tertiary base olen-H2S reaction. This factor of the' molar ratio of the reactants naturally will be regulated by the economics of the particular c ase at hand, that is, by the relative costs of hydrocarbon and HiS, and of their handling and recovery.

While it is possible. and is contemplated herein, to use the catalyst without a catalyst support, it is preferred that the catalyst be supported on an adsorbent inert carrier. Many such substances may be used for this purpose,-typical of which are wood charcoal, cocoanut charcoal,

. granulated coke, certain clays which are catsilica gel, etc. For example, we have found that wood and cocoanut charcoals exert little, if any. catalytic effect in themethods of separation and preparation contemplated herein. Wood charcoal, under the same conditions used in obtaining the results shown by the curve in Figure 3, had no catalytic effect.

From the foregoing description and examples, it will be .seen that the process contemplated herein provides a convenient means for separating tertiary base olefins from a mixture of hydrocarbons which are to be used in subsequent procedures where the tertiary base olefin would be an undesirable contaminant. It also provides an economical process for the synthesis of tertiary mercaptans, such as tertiary butyl mercaptans and tertiary amyl mercaptan from either a hydrocarbon mixture containing the corresponding tertiary base olefin or the corresponding tertiary base olen in the pure form. If the hydrocarbon reactant contains several tertiary base olefins, the mercaptan product will be a mixture oi the corresponding tertiary mercaptans which can be separated into its various components by fractionation.

It is to be understood that thi-s invention' is not t be limited to the foregoing typical illustrative examples of the same, but is to be construed broadly as defined by the language of the appended claims.

We claim:

1. The method of making a, tertiary mercaptan from a tertiary base olefin selected from the group consisting of isobutylene, trimethyl ethylene and unsymmetrical methyl ethyl ethylene which comprises, passing said tertiary base olefin in the vapor phase with hydrogen sulfide through a reaction zone containing elementary phosphorus, regulating the ow of said reactants through said reaction zone to provide therein a contact time from a fraction of a second to several minutes and maintaining the temperature of said reactants therein between about 25 C. and about 200 C.,

whereby 'said tertiary base olefin is converted to the corresponding teritary mercaptan.

2. The method of making a tertiary mercaptan from a tertiary base olen selected from the group consistingof is'obutylene, trimethyl ethylene and unsymmetrical methyl ethyl ethylene which comprises, passing said tertiary base olen in the vapor phase with hydrogen sulde through a reaction zone containing red phosphorus, regulating the ow of said reactants through said reaction zone to provide therein a contact time from a fraction of a second to several minutes and 4maintaining the temperature of said reactants therein between about 25 C. and about 200 C., whereby said tertiary base olen is converted to the corresponding tertiary mercaptan.

l3. The method of making a tertiary mercaptan from a tertiary base olefin selected from the group consisting of isobutylene, trimethyl ethylene and unsymmetrical methyl ethyl ethylene which comprises, passing said tertiary base olefin in the vapor phase with hydrogen suldethrough a reaction zone containing red phosphorus, regulating the ow of said reactants through said reaction zone to provide therein a contact time from a fraction of a second to several minutes and maintaining the temperature of said reactants therein 'between about 35 C. and about 85 C., whereby said tertiary base olen is converted to the corresponding tertiary mercaptan.

4. The method of making a tertiary mercaptan from a tertiary base olen selected from the group action zone containing red phosphorus, regulating the flow of said reactants through said reaction zone to provide therein a contact time from a fraction of a second to several minutes and maintaining the temperature of said reactants therein at about 55 C. whereby said tertiary base olen is converted to the corresponding tertiary mercaptan.

5. The method of making tertiary butyl mercaptan from isobutylene which compriseapassing said isobutylene in the vapor phase with hydrogen sulfide through a reaction zone containing red phosphorus, regulating the flow of said reactants through said reaction zone to provide therein a contact time from a. fraction of a second to several minutes and maintaining the temperature of said reactants therein between about 35 C. and about C., whereby said isobutylene is converted to tertiary butyl mercaptan.

6. The method of making tertiary amyl mercaptan from trimethyl ethylene which comprises, passing said trimethyl ethylene in the vapor phase with hydrogen sulfide through a reaction zone containing red phosphorus,l regulating the fiow of said reactants through said reaction zone to provide therein a contact time from a fraction of a second to several minutes and maintaining the temperature of said reactants therein between about 35 C. and about 85 C., whereby said trimethyl ethylene is converted to tertiary amyl mercaptan.

7. The method of making tertiary amyl mercaptan from unsymmetrical methyl ethyl ethylene which comprises, passing said unsymmetrical methyl ethyl ethylene in the vapor phase with hydrogen sulfide through a reaction zone containing red phosphorus, regulating the flow of said reactants through said reaction zone'to provide therein a contact time from a fraction of a second to several minutes and maintaining the temperature of said reactants therein between about 35 C. and about 85 C., whereby said unsymmetrical methyl ethyl ethylene is converted to tertiary amy] mercaptan.

8. The method of selectively separating a tertiary base olefin selected from the group consisting of isobutylene, trimethyl ethylene and unmixing said hydrocarbon mixture with hydrogensulfide; passing the reaction mixture thus formed in the vapor phase through a reaction zone containing elementary phosphorus, regulating the flow of said reaction mixture through said reaction zone to provide therein a very brief contact time therein and maintaining the temperature of said reaction mixture therein between about 25 C. and about 200 C., whereby said tertiary base olefin is converted to the corresponding tertiary mercaptan; and separating said mercaptan from the reaction product so obtained.

9. The method of selectively separating a tertiary base olefin selected from the group consisting of isobutylene, trimethyl ethylene and unsymmetrical methyl ethyl ethylene from a hydrocarbon mixture containing said tertiary base olen, a normal olen, a secondary olen and a saturated hydrocarbon, which comprises: admixing said hydrocarbon mixture with hydrogen sulnde: passing thoreaction mixture thus formed therein and maintaining the temperature of said reaction mixture therein between about 25 C.

and about 200 C., whereby said tertiary base.

olefin is converted to the corresponding tertiary mercaptan; and separating said mercaptan from the reaction product so obtained.

10. The method of selectively separating a tertiary base olen,selected from the group consisting of isobutylene, trimethyl ethylene and unsymmetrical methyl ethyl ethylene from a hydrocarbon mixture containing said tertiary base 01eiin, a normal olein, a secondary olen and a saturated hydrocarbon, which comprises: admixing said hydrocarbon mixture with' hydrogen suliide; passing the reaction mixture thus formed in the vapor phase through a reaction zone containing red phosphorus, regulating the flow of said reaction mixture through said reaction zone to provide therein a very brief contact time therein and maintaining the temperature of said reaction mixture therein between about 35 C.

and about 85 C., whereby said tertiary base olen is converted to the corresponding tertiary mercaptan; and separating said mercaptan the reaction product so obtained.

11. The method of selectively separating a tertiary base olen selected from the group cone from sisting of isobutylene, trimethyl ethylene and un-4 symmetricai methyl ethyl ethylene from a hydrocarbon mixture containing said tertiary base olefin, a normal olefin, a secondary olefin and a saturated hydrocarbon, which comprises: admixing said hydrocarbon mixture with hydrogen sulfide; passing the reaction mixture thus f ormed in the vapor phase through a reaction zone containing red phosphorus, regulating the ow of said reaction mixture through said reaction zone to provide therein a very brief contact time therein and maintaining the temperature of said reaction mixture therein at about 55 C., whereby said tertiary base oleiin is converted to the corresponding tertiary mercaptan; and separatf ing said mercaptan from the reaction product so obtained. l Y

12. In a method for making a tertiary mercaptan by reacting a monomeric tertiary base olen vapor with hydrogen sulfide in the presence of elementary phosphorus, the improvement which comprises: regulating the iiow of saidY sulfide through a reaction' zone containing ele- .mentary phosphorus, the improvement which comprises: regulating the ilow of said vapor phase mixture through said reaction zone to provide a contact time therein 'from a fraction oi a second to several minutes and maintaining the temperature of said vapor phase mixture therein between about 35 C. and about 85 C.

.14. The method of making a tertiary mercaptan from a monomeric tertiary base olen which comprises, passing said oleiin in the vapor phase with hydrogen sulfide through a reaction zone containing elementary phosphorus, regulating the flow of said reactants through said reaction zone to provide therein a contact time from a fraction of asecond to several minutes and maintaining the temperature of said reactants therein betweenabout 25 C. and about 200 C., whereby said olefin is converted to the corresponding 30 tertiary mercaptan.

15. The method of selectively separating a tertiary base oleiin select'ed from the group consisting of isobutylene, trimethyl ethylene and unsymmetrical methyl ethyl ethylene from a hydrocarbon mixture containing said tertiary base olein and at least one non-tertiary base olefin, which comprises: admixing said hydrocarbon mixture with hydrogen sulfide; passing the reaction mixture thus formed in the vapor phase 40 through a reaction zone containing elementary 

